The present invention relates to heat transfer mechanisms, and more particularly, to cooling apparatuses, cooled electronic modules and methods of fabrication thereof for removing heat generated by one or more electronic devices. Still more particularly, the present invention relates to cooling apparatuses and methods employing a plurality of thermally conductive fins extending from a thermally conductive base attached to a surface to be cooled, for example, of a heat-generating electronic module.
As is known, operating electronic devices produce heat. This heat should be removed from the devices in order to maintain device junction temperatures within desirable limits, with failure to remove the heat resulting in increased device temperatures, potentially leading to thermal runaway conditions. Several trends in the electronics industry have combined to increase the importance of thermal management, including heat removal for electronic devices, including technologies where thermal management has traditionally been less of a concern, such as CMOS. In particular, the need for faster and more densely packed circuits has had a direct impact on the importance of thermal management. First, power dissipation, and therefore heat production, increases as device operating frequencies increase. Second, increased operating frequencies may be possible at lower device junction temperatures. Further, as more and more devices are packed onto a single chip, heat flux (Watts/cm2) increases, resulting in the need to remove more power from a given size chip or module. These trends have combined to create applications where it is no longer desirable to remove heat from modern devices solely by traditional air cooling methods, such as by using air cooled heat sinks with heat pipes or vapor chambers. Such air cooling techniques are inherently limited in their ability to extract heat from an electronic device with high power density.
The need to cool current and future high heat load, high heat flux electronic devices therefore mandates the development of aggressive thermal management techniques, such as using liquid cooling. Various types of liquid coolants provide different cooling capabilities. In particular, fluids such as refrigerants or other dielectric liquids (e.g., fluorocarbon liquid) exhibit lower thermal conductivity and specific heat properties, when compared to liquids such as water or other aqueous fluids. Dielectric liquids have an advantage, however, in that they may be placed in direct physical contact with electronic devices and interconnects without adverse affects such as corrosion or electrical short circuits. Other cooling liquids, such as water or other aqueous fluids, exhibit superior thermal conductivity and specific heat compared to dielectric fluids. Water-based coolants, however, must be kept from physical contact with electronic devices and interconnects, since corrosion and electrical short circuit problems are likely to result from such contact. Various methods have been disclosed in the art for using water-based coolants, while providing physical separation between the coolants and the electronic device(s). With liquid-based cooling apparatuses, however, it is still necessary to attach the cooling apparatus to the electronic device. This attachment results in a thermal interface resistance between the cooling apparatus and the electronic device. Thus, in addition to typical liquid cooling issues regarding sealing, clogging due to particulate contamination, thermal conductivity of the cooling apparatus, effectiveness of the interface to the electronic device as well as the thermal expansion match between the cooling apparatus and the electronic device and manufacturability, need to be addressed. The invention disclosed herein presents a high-performance liquid cooling apparatus and method of fabrication that addresses the above-noted considerations for liquid-cooling-based apparatuses.